Stability and tracking analysis of gas face seals under low-parameter conditions considering slip flow

Abstract

Dynamic property of a gas face seal is about an internal ability of the mass-spring-damper system consisting of the nonlinear gas film, the flexible support, and the component mass or moment of inertia to handle ambient disturbances. Stability and tracking properties are important dynamic components, the current research for which mainly focuses on high-speed and high-pressure conditions in turbomachinery applications. In this paper, perturbation theory is used to obtain the linearized properties of the gas film in a spiral groove gas face seal, where the Boltzmann-Reynolds model with Fukui-Kaneko approximation is involved to account for slip flow under low-parameter conditions. Transmissibility of the step jump method is introduced into the perturbation method, and a critical ambient-disturbance amplitude is further proposed to cover the defect of transmissibility in characterizing the tracking property. The effects of slip flow on the stability and tracking properties of gas face seals are explored. The results show that slip flow induces an extra "relaxation region" in the critical transverse moment of inertia, providing a softer demand for angular stability. With regard to transmissibility, slip flow will induce an advantageous effect on transmitting the rotor motion to the stator. However, after considering the space required for tracking motions, the results of critical amplitude indicate that slip flow will induce an extra "rigorous region", leading gas face seals to require more conservative design and more rigorous manufacture and assembly for non-contacting tracking.

The parametric analysis on angular vibration stability of spiral groove dry gas seal with real gas model

“…According to the vibration mechanics theory, the vibration system is in a critical state when the real parts of characteristic solutions are equal to zero for formula (11). Thus, the stability thresholds for the stator angular oscillation are given by the following…”

“…In the current model, the general solutions of stator angular motion equation are assumed to be α s ( t * ) = α ε e s t * and β s ( t * ) = β ε e s t * . Subsequently, the dynamic equation used for the angular vibration stability investigation is expressed as 11,22…”

“…In this study, due to the stability of DGSs in axial direction is not an essential content to be further explored, 11,14 the influence of real gas effect on the angular stability of S-DGS at different operating parameters (e.g. entrance pressure and rotating speed) and S-DGS angular vibration thresholds with varying structural parameters (e.g.…”

“…By employing the finite element method, Zhang 10 investigated the influence of supplying pressure on the stability for a dynamic-hydrostatic hybrid lubrication DGS, and found that the vibration stability of pumping outward DGS is greater than that of pumping inward DGS. Hu et al 11 revealed the mechanism that critical transverse moment of inertia influenced by slip flow effect. They demonstrated that the slip flow effect enlarges the critical transverse moment of inertia, and the deviation between slip flow and non-slip flow models reduces as rotating speed increases.…”

Analysis on the dynamic characteristics of spiral groove dry gas seal based on the gas film adaptive adjustment model

“…Dry gas seal (DGS) is a rapidly developing sealing technology, and enhancing its stability characteristic plays an important role in improving the efficiency of the main engine (Xu, 2019). As the core component of rotating machineries in petroleum chemical and energy power industries, the main reason of sealing failure is dynamic instability (Hu et al , 2017). It is difficult to fully meet the design guidance requirements only by considering the steady sealing performance.…”